www.ijatir.org ISSN 2348–2370 Vol.07,Issue.07, July-2015, Pages:1194-1202 Copyright @ 2015 IJATIR. All rights reserved. Improve Performance on AC Fault Ride through in Multiterminal HVDC Grids K. AJAY KUMAR 1 , CH. PRATHYUSHA 2 1 PG Scholar, Vaageswari College of Engineering, Ramakrishna Colony, Karimnagar(Dt), Telangana, India. 2 Assistant Professor, Vaageswari College of Engineering, Ramakrishna Colony, Karimnagar(Dt), Telangana, India. Abstract: A totally operational multi terminal dc (MTDC) grid can play the strategic position for mainland ac techniques interconnection and to integrate ocean going wind plants. The incredible importance of such structure requires the compliance using fault trip through (FRT) capability in case of mainland air conditioning unit faults. In order to provide FRT ability in MTDC grids, communication-free innovative control functionalities exploiting a couple of local control rules with the converter channels and wind generators are determined. The suggested control functionalities are responsible for mitigating this dc voltage surge effect resulting from the lowering of lively power treatment into onshore air conditioning unit systems through grid mistakes. The suggested strategies envision an easy control in the wind wind turbine active power output like a function in the dc grid voltage surge and make up alternative options to prevent the using classical solutions while using installation of chopper resistors from the MTDC grid. The feasibility as well as robustness in the proposed techniques are exhibited and discussed from the paper within different circumstances. Keywords: Fault Trip Through (FRT), HVDC, VSC, MTDC. I. INTRODUCTION The development of additional electrical interconnect- ions is presently being planned by sea exploiting offshore grids, as it is documented in the European project ―Twenties‖ and in the Intelligent Energy Europe projects ―OffshoreGrid‖ and ―TradeWind‖. In both cases, offshore interconnections are expected to provide two main requirements: the support to exchange power between ac areas and offshore wind power integration. The ac transmission of bulk power over long distances in offshore interconnections is technically limited by the high capacitance of shielded power cables. High-voltage direct current–voltage-source converter (HVDC–VSC) technology seems to be the most promising solution for offshore dc connections since it uses small harmonic filters, it allows the independent control of active and reactive power, bidirectional power flows, voltage support and it is able to provide black-start capability . Regarding HVDC transmission, multiterminal dc (MTDC) grids are foreseen as an alternative solution to point-to-point connections, providing higher flexibility, increased redundancy and reduction of maximum power not supplied to onshore grids in case of dc disturbances.A fully operational MTDC grid with offshore wind farms (WF) can be regarded as a large (virtual) power plant capable of providing ancillary services to mainland ac grids [1]. In this sense, it is expected that MTDC grids also provide fault ride through (FRT) capability for faults occurring in the mainland ac grid, in line with grid code requirements for onshore wind generators [2]. The analysis and performance evaluation of different control solutions for the provision of FRT requirements in point-to-point HVDC systems equipped with VSC. In any case, the dc voltage rise due to the onshore VSC power transfer reduction during the ac grid fault is the major concern for the development of any control strategy. the authors propose five methodologies to dissipate/accommodate dc grid power in order to control the dc voltage rise. Excepting the solution based on the installation of dc chopper resistors, the other methodologies rely on a fast communication channel between onshore and offshore converter/wind turbine and involve: active power reduction output through offshore converter current control, wind turbine power set-point adjustment, offshore grid frequency adjustment and offshore ac grid voltage controlled reduction. the authors propose a strategy to control the dc voltage rise during the ac grid fault by de-loading the offshore WF proportionally to the dc voltage rise. However, this strategy assumes the use of a communication link between the offshore converter and each wind turbine. Also, the installation of dc grid chopper resistor has been contemplated as an alternative. III. HIGH-VOLTAGE, DIRECT CURRENT (HVDC) A. Introduction A high-voltage, direct current electric power transmission system uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current (AC) systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance each cycle. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be warranted, due to other benefits of direct current links. HVDC allows power transmission between unsynchronized AC transmission
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www.ijatir.org
ISSN 2348–2370
Vol.07,Issue.07,
July-2015,
Pages:1194-1202
Copyright @ 2015 IJATIR. All rights reserved.
Improve Performance on AC Fault Ride through in Multiterminal HVDC Grids K. AJAY KUMAR
1, CH. PRATHYUSHA
2
1PG Scholar, Vaageswari College of Engineering, Ramakrishna Colony, Karimnagar(Dt), Telangana, India.
2Assistant Professor, Vaageswari College of Engineering, Ramakrishna Colony, Karimnagar(Dt), Telangana, India.
Abstract: A totally operational multi terminal dc (MTDC)
grid can play the strategic position for mainland ac
techniques interconnection and to integrate ocean going
wind plants. The incredible importance of such structure
requires the compliance using fault trip through (FRT)
capability in case of mainland air conditioning unit faults.
In order to provide FRT ability in MTDC grids,
communication-free innovative control functionalities
exploiting a couple of local control rules with the converter
channels and wind generators are determined. The
suggested control functionalities are responsible for
mitigating this dc voltage surge effect resulting from the
lowering of lively power treatment into onshore air
conditioning unit systems through grid mistakes. The
suggested strategies envision an easy control in the wind
wind turbine active power output like a function in the dc
grid voltage surge and make up alternative options to
prevent the using classical solutions while using
installation of chopper resistors from the MTDC grid. The
feasibility as well as robustness in the proposed techniques
are exhibited and discussed from the paper within different
circumstances.
Keywords: Fault Trip Through (FRT), HVDC, VSC,
MTDC.
I. INTRODUCTION The development of additional electrical interconnect-
ions is presently being planned by sea exploiting offshore
grids, as it is documented in the European project
―Twenties‖ and in the Intelligent Energy Europe projects
―OffshoreGrid‖ and ―TradeWind‖. In both cases, offshore
interconnections are expected to provide two main
requirements: the support to exchange power between ac
areas and offshore wind power integration. The ac
transmission of bulk power over long distances in
offshore interconnections is technically limited by the
high capacitance of shielded power cables. High-voltage
direct current–voltage-source converter (HVDC–VSC)
technology seems to be the most promising solution for
offshore dc connections since it uses small harmonic
filters, it allows the independent control of active and
reactive power, bidirectional power flows, voltage
support and it is able to provide black-start capability .
Regarding HVDC transmission, multiterminal dc
(MTDC) grids are foreseen as an alternative solution to